The invention disclosed and claimed herein relates to electronic thermometry. More specifically, the invention relates to apparatus for and method of measuring temperature with a monitor remote from the environment the temperature of which is sought to be measured and is adapted to receive temperature information from a transmitter in close thermal communication with such environment.
It is known in the art of clinical thermometry to use both glass and electronic thermometric devices. Both such known types of devices are inherently inaccurate, both lend themselves to cross-contamination, both devices are time-consuming to use and both require that the patient be awake or at least be disturbed while temperature is being taken. Even in monitoring the temperature of inanimate objects, present technology suffers from like deficiencies.
Prior art electronic thermometry has improved the art of thermometry, but still with certain disadvantages. For example, it is known in the art of remote electronic thermometry to vary the duty cycle of the waveform of electromagnetic energy transmitted indicative of temperature by employing a temprature sensitive element in close thermal communication with an environment, such as a human body, the temperature of which is sought to be measured, and to measure the duty cycle of the energy received by a monitor placed remotely from the subject whose temperature is to be measured to obtain an indication of the body temperature. Such thermometry systems generally employ a temperature sensitive circuit element such as a thermistor in the time constant circuit of a multivibrator to vary the duty cycle of the multivibrator as a function of temperature. Typical of such prior art arrangements are U.S. Pat. No. 3,453,546 to Fryer for Telemeter Adaptable For Implanting In an Animal, U.S. Pat. No. 3,921,621 to Baessler for Method And System Utilizing A Disposable Transmitter For Monitoring A Patient's Condition, U.S. Pat. No. 3,940,752 to Bair for Transducing System and U.S. Pat. No. 3,971,362 to Pope, et al for Miniature Ingestible Telemeter Devices To Measure Deep-Body Temperature. An inherent characteristic of the prior art remote thermometry systems which employ temperature variable time constant multivibrator circuits is a corresponding variation in the frequency as well as the duty cycle of the temperature information containing waveforms. Such systems are disadvantageous in requiring relatively broad transmission bandwidths and, hence, are susceptible to interference from spurious noise, harmonics and other transient effects. In addition, the monitor circuitry employed to receive the temperature information containing transmissions and to decode the transmissions into usable thermometry data are sometimes complex, expensive, and unreliable.
It is also known in the art to transmit information by varying the duty cycle of a constant frequency waveform for purposes of effecting remote control of an electrical device. Such a system is disclosed in U.S. Pat. No. 2,462,134 to Scully for Remote Control Arrangements. Such devices rely on the balancing of a transmitted waveform having a duty cycle indicative of the desired control with respect to a locally generated waveform derived from the functions to be controlled. While such arrangements are useful in obtaining a desired degree of control in an electromechanical system, they do not provide for the transmission and comprehension of intelligence such as thermometry data.